The invention is in the field of "curb feelers." A lot of different devices have been conceived for this purpose, the simplest and the one which has principally been implemented being no more than a length of wire or coiled sheet metal which scrapes against the curb, alerting the driver by its scraping sound that the curb has been touched. This type of proximity indicator is useless to the driver of a recreational vehicle, and many cars as well, because the driver cannot hear the noise made by the scraper. Although units have been conceived which utilize an electrical alarm of some type, often these designs are problematic either in that they are too complicated to be practical, or because of the nature of the electrical contact. Another problem experienced with recreational vehicles is the need for a longer probe than conventional curb scrapers have. The length also must be variable, inasmuch as different vehicles, and even different mountings on the same vehicle, would require a different length. There is a real need for some type of inexpensive, reliable sensor having a signal that can be heard or seen from inside the driving compartment. This can be attested to by any car dealer, who has seen many misaligned front wheels resulting from the new driver being unable to judge wheel location. The same is true of many recreational vehicle drivers.